The African trypanosome, Trypanosoma brucei, is a protozoan parasite of medical and veterinary importance. The mitochondrion of T. brucei is able to undergo a life-cycle stage regulated biogenesis. In proliferative bloodstream forms, the mitochondrion is narrow, tubular and repressed since only glycolysis is required to provide energy for trypanosome survival. Over the course of two successive life-cycle stage differentiations, the trypanosome mitochondrion undergoes a biogenesis in which mitochondrial structure elaborates to support Kreb's cycle enzymes and fully functional cytochrome mediated oxidative phosphorylation. Mitochondrial homologs of dnaK (hsp70), dnaJ are the constituents of a universal chaperone machine central to the biogenesis of mitochondria. Disruption of the expression of these genes will have an effect on how the mitochondrion is constructed and may be able to prevent the mitochondrion being formed at all. In most eukaryotes dramatic disruption of mitochondrial biogenesis is lethal, however in the long slender form of the African trypanosome the repressed mitochondrion may not be an essential organelle. The African trypanosome is therefore likely to be a permissive system in which to dissect the functional relationships of these molecules. During the last year I have been successful in cloning and sequencing the T. brucei homolog of mitochondrial hsp70 and a novel mitochondrial dnaJ (tbmJ1). This grant will focus the basic characterization of tbmj1 expression, on the interactions of tbmj1 with tbmhsp70 and with other proteins, and on the effects of modulating the expression of the tbmj1 gene.